U.S. Pat. No. 4,668,339 entitled "Process For Dry Deinking of Secondary Fiber Sources" issued to Byron R. Terry describes a unique method of deinking wastepaper. The method resulted from the discovery that ink particles can be dislodged from wastepaper fibers by dry fiberization if the fiberization is carried out to the extent that the wastepaper is reduced to substantially individual fibers and fines. In the process much of the ink is reduced to ink particles and ink-containing fines, which can be simply removed by dry separation using a variety of separation means, such as screens or other related cleaning devices.
Although the process of Terry works well, it has been discovered that at high fiberizer throughputs, much of the wastepaper ink agglomerates into visible ink specks which do not readily separate by dry or conventional wet methods. In fact, the nature and numbers of these ink agglomerates sometimes can be such that the fiberized material actually appears to be dirtier than the original starting material fed to the fiberizer. It is postulated that at high fiberizer throughputs, heat is generated within the fiberizer which causes the dislodged ink particles to agglomerate to each other and to bind to the fibers. The nature and shape of the resulting particles is such that they are not easily removed from the fibers. Hence there is a need for a method capable of removing these agglomerated ink-particles from the acceptable fibers produced by a dry fiberization deinking process.